1. Field of the Invention
This invention relates to gas generation and more particularly relates to gas generation from solid reactant pouches.
2. Description of the Related Art
The portable generation of various gasses has many uses. Hydrogen is a desirable energy source. Oxygen has medical and emergency uses, as well as industrial uses. Hydrocarbon gasses, such as methane, are also desirable energy sources. Producing pure gasses using conventional methods is generally cost prohibitive or requires storing the gas at high pressures.
One way that pure gasses can be generated is through a chemical reaction which produces molecules of the desired gas. The chemical reaction that occurs between water (H2O) and chemical hydrides produces pure hydrogen. Chemical hydrides are molecules comprising hydrogen and one or more alkali or alkali-earth metals, or other elements. Chemical hydrides can produce large quantities of pure hydrogen when reacted with water.
Recently, the interest in hydrogen generation has increased, because of the development of lightweight, compact Proton Exchange Membrane (PEM) fuel cells. One by-product of generating electricity with a PEM fuel cell is water, which can be used or reused to produce pure hydrogen from chemical hydrides for fuelling the PEM fuel cell. The combination of PEM fuel cells with a chemical hydride hydrogen generator offers advantages over other energy storage devices in terms of gravimetric and volumetric energy density. Interest in portable and local generation of other gasses has also increased.
Unfortunately, there are several unresolved problems producing pure gasses from chemical reactions. Specifically, conventional systems, methods, and apparatuses have not successfully controlled chemical reactions between reactants without adversely affecting the gravimetric and volumetric energy density of the overall system. This lack of control also prevents conventional systems, methods, and apparatuses from meeting dynamic gas demands of new devices like PEM fuel cells.
Many chemical reactions that produce gasses are very severe and highly exothermic. The combination of reactants must be precisely controlled to prevent a runaway reaction or an explosion. Many failed attempts have been made to properly control the reactions while still preserving the gravimetric and volumetric energy density provided by the reactants.
Another side effect of such a system is that the reactants will “gum” or “clump” as the reactants are introduced. Gumming or clumping refers to the clumps formed by the reactants and their byproducts during the reaction. Often, a liquid reactant is able to react with the outer portion of the “clump” to a certain depth, while large portions of the “clump” remain un-reacted. Consequently, the gravimetric and volumetric energy density is decreased because of the large percentage of reactants that remain un-reacted. This is inefficient and greatly increases the amount of reactants that such systems use to create a given amount of gas.